1. Field of the Invention
The present invention relates to a stacked-type evaporator incorporated in an air-conditioner, particularly an air-conditioner for an automobile to cool air for air-conditioning the air inside a vehicle compartment.
2. Description of the Related Art
An evaporator, for evaporating a refrigerant to cool the air flowing over it, is incorporated in an air-conditioner for an automobile. As such an evaporator incorporated in the air-conditioner for an automobile, a so-called stacked-type evaporator is conventionally known which is constructed by stacking together a plurality of metal plates, as known in JP-A-62-798, JP-A-7-12778U, and JP-A-9-318195. This stacked-type evaporator is constructed by stacking together a plurality of heat transfer tube elements each formed by combining two metal plates in the form of a peapod. FIGS. 8 and 9 show a stacked-type evaporator having the structure disclosed in JP-A-9-318195 mentioned above.
This evaporator 1 is arranged such that a plurality of heat transfer tube elements 3 each having two flat independent channels 2 inside it are provided as metal plates in which two metal plates each having a recessed portion on a respective one surface thereof are set as a set and are superposed in the form of a peapod with their recessed portions aligned with each other, and are joined to each other airtightly and fluid-tightly. A core section 5 is formed by stacking the plurality of heat transfer tube elements 3 with fins 4 provided between adjacent ones of the heat transfer tube elements 3. In addition, first and second outer members 6 and 7 each formed by superposing a side plate and a metal plate are respectively disposed on widthwise both end portions of the core section 5 with the fins 4 interposed between the respective outer member and the outermost heat transfer tube element 3. Further, a plurality of tank portions 8 to 10 are formed by allowing adjacent ones of tank spaces provided in upper and lower end portions of the channels 2 inside the heat transfer tube elements 3, excluding some tank spaces, to communicate with each other. In addition, a side tank portion 11 for allowing two tank portions 8 of the plurality of tank portions 8 to 10 to communicate with each other is provided at one widthwise end portion (a left end portion in FIGS. 8 and 9) of the core section 5. This side tank portion 11 is formed inside the first outer member 6 provided at one widthwise end of the core section 5. In addition, an inlet-side passage 12 communicating with the inlet tank portion 9 and an outlet-side passage 13 communicating with the outlet tank portion 10 are respectively formed inside the second outer member 7 provided at the other widthwise end (a right end in FIGS. 7 and 8) of the core section 5. Further, a refrigerant feeding pipe 14 and a refrigerant fetching pipe 17 are connected to a portion of the second outer member 7 in a state of communication with the inlet-side passage 12 and the outlet-side passage 13, respectively.
When the evaporator 1 is used, the refrigerant in a liquid state or in a gas-liquid mixed state which has been fed into the inlet tank portion 9 through a refrigerant feeding port 15 provided in the refrigerant feeding pipe 14 is made to flow through the channels 2 making up the core section 5, and the refrigerant is evaporated in the core section 5, thereby lowering the temperate of the core section 5. At that time, the refrigerant circulated in the core section 5 is also circulated in the side tank portion 11. Further, as the air for air-conditioning is made to flow in the direction of arrow a in FIG. 9 with respect to the thicknesswise direction of the core section 5, this air is cooled. In addition, the gaseous refrigerant which evaporated in the core section 5 is fetched from the outlet tank portion 10 to the outside through a refrigerant fetching port 16 provided in the refrigerant fetching pipe 17, and is fed to an unillustrated compressor. Meanwhile, in the case of the stacked-type evaporator disclosed in JP-A-9-318195 mentioned above, the number of times (three times) the refrigerant fed into a thicknesswise one half portion (a front-side half portion in FIG. 9) the core section 5 where the inlet tank portion 9 is present is turned back in an opposite direction concerning the vertical direction through the tank portions 8 and 9 provided in this thicknesswise one half portion is made more numerous than the number of times (one time) the refrigerant fed into a thicknesswise other half portion (a back-side half portion in FIG. 9) of the core section 5 where the outlet tank portion 10 is present is turned back in the opposite direction concerning the vertical direction through the tank portions 8 provided in this thicknesswise other half portion.
In the case of the stacked-type evaporator disclosed in JP-A-9-318195 mentioned above in which heat exchange is effected between the refrigerant flowing inside the core section 5 and the air passing over outer portions of the core section 5 to effect the air, it is possible to increase the flow rate of the refrigerant in the thicknesswise one half portion of the core section 5 on the inlet tank portion 9 side where the liquid refrigerant flows in a large quantity inside it. For this reason, even under the condition where the cooling load is small, the refrigerant in a gas-liquid mixed state flowing in the thicknesswise one half portion of the core section 5 can be made difficult to be separated into a gaseous state and a liquid state in this thicknesswise one half portion. At the same time, the non-uniform flow distribution of the refrigerant in this thicknesswise one half portion can be made difficult to occur, and the pressure loss can be reduced to some extent. In contrast, in the thicknesswise other half portion of the core section 5 on the outlet tank portion 10 side where the gaseous refrigerant flows in a large quantity inside it, the number of the channels 2 where the refrigerant is distributed from the respective tank portions 8 is made numerous. Accordingly, the increase in the pressure loss based on the fact that the gaseous refrigerant flows in a large quantity inside the thicknesswise other half portion of the core section 5 can be suppressed to a low level.
In the case of the structure disclosed in JP-A-9-318195 mentioned above, there is a possibility that the performance of the evaporator 1 cannot be sufficiently ensured without rendering the evaporator 1 large in size. Namely, with the above-described conventional evaporator 1, the side tank portion 11 is provided at one widthwise end of the core section 5, and since the arrangement provided is such that all the refrigerant fed into the thicknesswise one half portion of the core section 5 flows inside the side tank portion 11, the pressure loss inside this side tank portion 11 possibly becomes large. In contrast, it is conceivable to reduce the pressure loss in the side tank portion 11 by making the cross-sectional area of the side tank portion 11 sufficiently large. This arrangement, however, causes the evaporator 1 to become large in size, so that it is not preferable.
In view of the above-described circumstances, the invention has been made to realize a structure that is compact and capable of sufficiently ensuring the performance.
In the same way as the conventionally known stacked-type evaporator, the stacked-type evaporator includes a core section formed such that two metal plates each having a recessed portion on a respective one surface thereof are set as a set and are superposed in the form of a peapod with their recessed portions aligned with each other, and are joined to each other airtightly and fluid-tightly so as to form each of a plurality of heat transfer tube elements each having flat channels inside it for allowing a refrigerant to flow therethrough, and the plurality of heat transfer tube elements are stacked with fins provided between adjacent ones of the heat transfer tube elements; a refrigerant feeding port for feeding the refrigerant into the core section; and a refrigerant fetching port for fetching the refrigerant from inside the core section. The stacked-type evaporator is used in a state in which the refrigerant is circulated in the heat transfer tube elements making up the core section, and air for air-conditioning is made to pass over outer portions of the heat transfer tube elements concerning a thicknesswise direction of the core section.
In particular, in the stacked-type evaporator of the invention, at least a widthwise portion of the core section is constructed by superposing in the widthwise direction a first section formed by stacking a plurality of first elements with the fins provided between adjacent ones of the first elements and a second section formed by stacking a plurality of second elements with the fins provided between adjacent ones of the second elements.
As each pair of first metal plates each having first and second deep recessed portions provided in a mutually independent state at a longitudinal one end portion of its respective one surface, third and fourth deep recessed portions similarly provided in a mutually independent state at a longitudinal other end portion of its respective one surface, a first shallow recessed portion similarly provided in its intermediate portion to allow the first and third deep recessed portions to communicate with each other, and a second shallow recessed portion similarly provided in its intermediate portion to allow the second and fourth deep recessed portions to communicate with each other are superposed in the form of the peapod with the first deep recessed portions opposed to each other and are jointed together, each of the first elements making up the first section is provided with a first tank space formed in a portion where corresponding ones of the first deep recessed portions are butted against each other, a second tank space formed in a portion where corresponding ones of the second deep recessed portions are butted against each other, a third tank space formed in a portion where corresponding ones of the third deep recessed portions are butted against each other, a fourth tank space formed in a portion where corresponding ones of the fourth deep recessed portions are butted against each other, a first linear channel formed in a portion where corresponding ones of the first shallow recessed portions are butted against each other so as to allow the first and third tank spaces to communicate with each other, and a second linear channel formed in a portion where corresponding ones of the second shallow recessed portions are butted against each other so as to allow the second and fourth tank spaces to communicate with each other.
Further, as each pair of second metal plates each having fifth and sixth deep recessed portions provided in a mutually independent state at a longitudinal one end portion of its respective one surface and a third shallow recessed portion similarly provided in its intermediate portion and turned up midway by 180 degrees to allow the fifth and sixth deep recessed portions to communicate with each other are superposed in the form of the peapod with mutually corresponding ones the deep recessed portions opposed to each other and are jointed together, each of the second elements making up the second section is provided with a fifth tank space formed in a portion where corresponding ones of the fifth deep recessed portions are butted against each other, a sixth tank space formed in a portion where corresponding ones of the sixth deep recessed portions are butted against each other, and a U-shaped channel formed in a portion where corresponding ones of the third shallow recessed portions are butted against each other so as to allow the fifth and sixth tank spaces to communicate with each other.
Furthermore, a plurality of tank portions are formed by causing adjacent ones of the first to sixth tank spaces, excluding some tank spaces, to communicate with each other in a state in which the first section made up of the first elements and the second section made up of the second elements are superposed.
In addition, the refrigerant, which has been fed into a thicknesswise one half portion of the core section through the refrigerant feeding port, flows through a portion of the plurality of tank portions, the first linear channels, and one half side portions of the U-shaped channels, which are respectively present in the thicknesswise one half portion of the core section, subsequently flows through a remaining portion of the plurality of tank portions, the second linear channels, and another side half portions of the U-shaped channels, which are respectively present in a thicknesswise other half portion of the core section, and is fetched from the refrigerant fetching port. The number of times the refrigerant fed into a thicknesswise one half portion of the first section which is present in the thicknesswise one half portion of the core section is turned back in an opposite direction concerning a longitudinal direction of the first linear channels inside the thicknesswise one half portion of the first section is made more numerous than the number of times the refrigerant fed into a thicknesswise other half portion of the first section is turned back in the opposite direction concerning the longitudinal direction of the second linear channels inside the thicknesswise other half portion of the first section.
In accordance with the stacked-type evaporator of the invention constructed as described above, it is possible to reduce the number of the first linear channels where the refrigerant is distributed from a portion of the plurality of tanks portions inside the thicknesswise one half portion of the first section making up a part of the core section. For this reason, since the flow rate of the refrigerant flowing through the first linear channels can be increased, the non-uniform flow distribution of the refrigerant between these first linear channels can be made difficult to occur, thereby making it possible to cool the thicknesswise one half portion of the first section substantially uniformly. In addition, the thicknesswise one half portion of the first section and the thicknesswise other half portion of the first section overlap with each other with respect to the flowing direction of the air for air-conditioning. Accordingly, even in a case where the temperature difference between the respective portions becomes large due to the fact that the degree of the non-uniform flow distribution of the refrigerant has become considerably large in the thicknesswise other half portion of the first section, or even if practically all the portions of the second linear channels provided in the thicknesswise other half portion are formed as superheat regions where the refrigerant with a high dryness fraction flows therethrough, it is possible to reduce the possibility that relatively high-temperature portions or relatively low-temperature portions overlap with each other with respect to the flowing direction of the air. For this reason, the temperature distribution of the air after passage over the core section can be made substantially uniform, so that a pleasant cooled state can be realized for an occupant of the vehicle.
Furthermore, in accordance with the invention, since the non-uniform flow distribution of the refrigerant in the thicknesswise one half portion of the first section can be made difficult to occur, it is possible to reduce the pressure loss and improve the performance of the evaporator. Moreover, since the number of the second linear channels where the refrigerant is distributed in the thicknesswise other half portion of the first section can be increased, it is possible to suppress to a low level an increase in the pressure loss based on the fact that a large quantity of gaseous refrigerant flows through these second linear channels. Further, the thicknesswise one half portion and the thicknesswise other half portion of the core section can be made to communicate with each other by means of the plurality of U-shaped channels provided inside the second section. For this reason, it becomes unnecessary to provide a side tank which can cause a rise in the pressure loss, so that it is possible to reduce the pressure loss further without enlarging the evaporator, thereby making it possible to ensure sufficient performance. Further, in accordance with the invention, as for the kinds of the elements making up the core section, only two kinds are used, so that a reduction of cost can be attained.